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x86/irq: Ensure initial PIR loads are performed exactly once

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[ Upstream commit 600e9606046ac3b9b7a3f0500d08a179df84c45e ]

Ensure the PIR is read exactly once at the start of handle_pending_pir(),
to guarantee that checking for an outstanding posted interrupt in a given
chuck doesn't reload the chunk from the "real" PIR.  Functionally, a reload
is benign, but it would defeat the purpose of pre-loading into a copy.

Fixes: 1b03d82ba1 ("x86/irq: Install posted MSI notification handler")
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20250401163447.846608-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Sean Christopherson
2025-04-01 09:34:40 -07:00
committed by Greg Kroah-Hartman
parent 1be2000b70
commit 2967178d30
1 changed files with 1 additions and 1 deletions
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2
arch/x86/kernel/irq.c
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@@ -414,7 +414,7 @@ static __always_inline bool handle_pending_pir(u64 *pir, struct pt_regs *regs)
bool handled = false;
for (i = 0; i < 4; i++)
pir_copy[i] = pir[i];
pir_copy[i] = READ_ONCE(pir[i]);
for (i = 0; i < 4; i++) {
if (!pir_copy[i])